1. Field of the Invention
The present invention relates to a resonant type capacitor charger that charges a load capacitor to a preset voltage cyclically, at high speed, and with high accuracy.
2. Description of the Related Art
Capacitor chargers are used for charging first stage capacitors of driving pulse power sources for driving pulse lasers such as a copper vapor laser, an excimer laser or the like, at high speed, repeatedly.
A capacitor charger is constructed such that an output of an inverter section IV is connected to a rectifier RE as shown in FIG. 10.
That is, the capacitor charger controls the power output from a dc voltage source DC, converts a direct current supplied from the dc voltage source DC into an alternating current (square wave ac voltage) using the inverter section IV, rectifies the alternating current boosted by a transformer H using the rectifier RE, and charges a load capacitor CD using this rectified current.
Then, a control section 100 controls the charging of the load capacitor CD, being a charged object, by measuring a measured voltage V10, which is proportional to a charging voltage value V1 of the load capacitor CD, using a voltage divider M1, and comparing the measured voltage V10 detected with a preset voltage V2 that indicates a target value of charging voltage of the load capacitor CD.
That is, the control section 100 determines whether the measured voltage V10 from the voltage divider M1 exceeds the internal preset voltage V2 or not. If exceeding, it stops the inverter section IV at this point of time and stops charging the load capacitor CD.
However, in a conventional capacitor charger, since it is necessary to satisfy the high speed required for a driving pulse laser, repeated charging at high speed is required, and hence it is necessary to increase the charging current to the load capacitor CD during a half cycle corresponding to one driving pulse driving the inverter section IV.
Therefore, there are problems in a conventional capacitor charger that since the charging voltage charged by the charging current in each half cycle becomes high, even if the inverter section IV is stopped at the time that the charging voltage of the load capacitor CD reaches the target value, it can easily overshoot, so control cannot be performed with high accuracy, and the output of the driving pulse laser is inconsistent.
On the other hand, in the above-described capacitor charger, if the number of driving pulses for driving the inverter section IV during the charge period is increased, and the charging voltage value V1 of the load capacitor CD and the preset voltage V2 are compared accurately, in order to perform a charging process with high accuracy, it is necessary to limit the charging voltage in one driving pulse.
By so doing, even if the accuracy of charging can be increased in the conventional capacitor charger, there is a disadvantage that the high speed charging required for a driving pulse laser cannot be satisfied.
The present invention takes this background into consideration with an object of providing a capacitor charger that can control charging voltage with high accuracy, and repeat a process of raising it to a target charging voltage at high speed.
A capacitor charging method according to a first aspect of the present invention is a capacitor charging method in which a resonant type inverter section is operated by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage, and a capacitor is charged using the dc voltage, comprising the steps of: a first step where a first type of driving pulse of the driving pulses has a fixed driving pulse width W1 determined in advance, which charges the capacitor by a boost voltage xcex94Vn (n is a natural number, step up voltages xcex94V1, xcex94V2, . . . that gradually decrease as a load capacitor CD is charged) at each input of the first type of driving pulse; and a second step which charges the capacitor by a single or a plurality of a second type of driving pulse having a controlled driving pulse width W2 (W1 greater than W2) as required to increase the voltage of the capacitor by a voltage [V2xe2x88x92V1] when a charging voltage V1 of the capacitor reaches a value that satisfies [V2 greater than V1 greater than V2xe2x88x92V1 less than xcex94Vn] for a target voltage value V2.
A capacitor charging method according to a second aspect of the present invention is a capacitor charging method in which a resonant type inverter section is operated by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage, and a capacitor is charged using the dc voltage, comprising the steps of: a first step where a first type of driving pulse of the driving pulses has a fixed driving pulse width W1 determined in advance, which charges the capacitor by a boost voltage xcex94Vn (n is a natural number, xcex94V1, xcex94V2, . . . ) at each input of the first type of driving pulse; and a second step which charges the capacitor by a plurality of a second type of driving pulse having a fixed driving pulse width W3 (W1 greater than W3) in order to boost the voltage by [V2xe2x88x92V1] when a relationship between a charging voltage V1 of the capacitor and a target voltage value V2 is [V2xe2x88x92V1 less than xcex94Vk+ . . . +xcex94Vn (k is a natural number, and k less than n), or [V2xe2x88x92V1 less than xcex94Vn].
In the capacitor charging method according to the second aspect of the present invention, only the last driving pulse among a plurality of the second type of driving pulses in the second step may have a controlled driving pulse width.
A capacitor charging method according to a third aspect of the present invention is a capacitor charging method in which a resonant type inverter section is operated by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage, and a capacitor is charged using the dc voltage, comprising the steps of: a first step where a first type of driving pulse of the driving pulses has a fixed driving pulse width W1 determined in advance, which charges the capacitor by a boost voltage xcex94Vn (n is a natural number, step up voltages xcex94V1, xcex94V2, . . . that gradually decrease as a load capacitor CD is charged) at each input of the first type of driving pulse; a second step which when a charging voltage V1 of the capacitor is a midpoint preset voltage value V3 that is lower than a target voltage value V2, charges by a boost voltage xcex94Vm (m is a natural number), by using a second type of driving pulse with a new, fixed driving pulse width W4 obtained with consideration of a change of input voltage to the resonant type inverter section; and a third step which charges by a third type of driving pulse having a controlled driving pulse width W5 (W5 less than W4) as required to boost the voltage by [V2xe2x88x92V1 less than xcex94Vm].
In the capacitor charging methods according to the present invention, at the start of charging of the first step, the capacitor may be charged by a fixed driving pulse width smaller than the fixed driving pulse width W1, or a soft start driving pulse with a gradually increasing driving pulse width.
A capacitor charger according to a first aspect of the present invention is a capacitor charger in which a resonant type inverter section is switched by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage by a rectifier, and a capacitor is charged using the dc voltage, comprising: a control section that controls such that the voltage of the capacitor is increased by a boost voltage xcex94Vn (n is a natural number, step up voltages xcex94V1, xcex94V2, . . . that gradually decrease as a load capacitor CD is charged) at each input to the resonant type inverter section of a first type of driving pulse with a predetermined, fixed driving pulse width W1, calculates an nth first type of driving pulse with the fixed driving pulse width W1 when a relationship between a charging voltage V1 of the capacitor and a target voltage value V2 satisfies [V2 greater than V1 greater than V2xe2x88x92V1 less than xcex94Vn] (n is a natural number), calculates at least one of a required adjusted driving pulse width and the number of driving pulses, of a second type of driving pulse that is supplied in order to increase the voltage of the capacitor by [V2xe2x88x92V1] when a relationship [V2xe2x88x92V1 less than xcex94Vn] is satisfied, drives the resonant type inverter section by the first type of driving pulse until the relationship [V2xe2x88x92V1 less than xcex94Vn] is satisfied for the charging voltage V1, drives the resonant type inverter section by the second type of driving pulse when the relationship [V2xe2x88x92V1 less than xcex94Vn] is satisfied, and charges the capacitor to the target voltage value V2.
A capacitor charger according to a second aspect of the present invention is a capacitor charger in which a resonant type inverter section is switched by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage by a rectifier, and a capacitor is charged using the dc voltage, comprising: a control section that controls such that the voltage of the capacitor is increased by a boost voltage xcex94Vn (n is a natural number, step up voltages xcex94V1, xcex94V2, . . . that gradually decrease as a load capacitor CD is charged) at each input to the resonant type inverter section of a first type of driving pulse with a predetermined, fixed driving pulse width W1, calculates an nth first type of driving pulse with the fixed driving pulse width W1 when a relationship between a charging voltage V1 of the capacitor and a target voltage value V2 satisfies [V2xe2x88x92V1 less than xcex94Vn+ . . . xcex94Vn+k] (k is a natural number, k less than n), or [V2xe2x88x92V1 less than xcex94Vn], calculates the number of driving pulses of a second type of driving pulse with a fixed driving pulse width W2 (W1 greater than W2) that is supplied in order to increase the voltage of the capacitor by [V2xe2x88x92V1] when a relationship [V2xe2x88x92V1 less than xcex94Vn+ . . . xcex94Vn+k] or [V2xe2x88x92V1 less than xcex94Vn] is satisfied, drives the resonant type inverter section by the first type of driving pulse until the relationship [V2 greater than V1 greater than V2xe2x88x92V1 less than xcex94Vn+ . . . xcex94Vn+k] or [V2xe2x88x92V1 less than xcex94Vn] is satisfied for the charging voltage V1, drives the resonant type inverter section by the second type of driving pulse when the relationship [V2 greater than V1 greater than V2xe2x88x92V1 less than xcex94Vn+ . . . xcex94Vn+k] or [V2xe2x88x92V1 less than xcex94Vn] is satisfied, and charges the capacitor to the target voltage value V2.
Here, xcex94Vn+ . . . +xcex94Vn+k represents the sum of voltages charged by respective driving pulses of a plurality of supplied driving pulses.
A capacitor charger according to a third aspect of the present invention is a capacitor charger in which a resonant type inverter section is switched by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage by a rectifier, and a capacitor is charged using the dc voltage, comprising: a control section that controls such that the voltage of the capacitor is increased by a boost voltage xcex94Vn (n is a natural number, xcex94V1, xcex94V2, . . . ) at each input to the resonant type inverter section of a first type of driving pulse with a predetermined, fixed driving pulse width W1, calculates an nth first type of driving pulse with the fixed driving pulse width W1 when a relationship between a charging voltage V1 of the capacitor and a midpoint preset voltage value V3, that is lower than a target voltage value V2, satisfies [V2xe2x88x92V1 less than xcex94Vn+ . . . xcex94Vn+k] (k is a natural number, and k less than n), drives the resonant type inverter section by a second type of driving pulse of a fixed driving pulse width W3 obtained by another calculation when the relationship [V2xe2x88x92V1 less than xcex94Vn+ . . . xcex94Vn+k] is satisfied, calculates a controlled pulse width or the number of controlled driving pulses of a third type of driving pulse when a relationship [V2xe2x88x92V1 less than xcex94Vp] (p is a natural number) is satisfied for the charging voltage V1 of the capacitor, drives the resonant type inverter section by the third type of driving pulse, and charges the capacitor to the target voltage value V2.
In the capacitor charger according to any one of the first to third aspects of the present invention, the control section may calculate the driving pulse width using a predetermined equation based on an input voltage value input to the capacitor charger, a voltage value of charging voltage V1, and a current value supplied to the capacitor.
In the capacitor charger according to any one of the first to third aspects of the present invention, the control section may read out from a lookup table showing a relationship between detected values of input voltage input to the capacitor charger, voltage values of the charging voltage V1, and current values supplied to the capacitor, and values of the driving pulse width, a driving pulse width value corresponding to these detected values, to thereby calculate the driving pulse width.
In the capacitor charger according to any one of the first to third aspects of the present invention, the control section may read out from a lookup table showing a relationship between detected values of input voltage input to the capacitor charger and the charging voltage V1, and values of the driving pulse width, a driving pulse width value corresponding to these detected values, to thereby calculate the driving pulse width.
According to the present invention, it is possible to obtain an adjusted driving pulse width with high accuracy, and obtain a final charging voltage V1 that has a smaller difference from the target voltage value V2.
Furthermore, according to the present invention, it is possible to charge to the target voltage value V2, being the final target of the charging voltage V1, at high speed.